The billionaire investor said Friday in a regulatory filing that he'll begin using Facebook, which he joined last month, to promote his activist campaigns. Icahn is already an avid user of Twitter and last year launched a website.

In the Securities and Exchange Commission filing, Icahn said he may post material non-public information on his Facebook page, as well as on Twitter and on his Shareholders' Square Table website. The SEC last year made clear that companies can use social media to disclose information, as long as they have specified the platforms they will use.

Icahn, who boasts more than 150,000 followers on Twitter, has already won 5,000 "likes" for his Facebook page.

From the current issue of

MODERN TRADER explores the effect of a potential trade war on U.S. equity markets. Will it end the bull run or will low interest rates allow U.S. equities to maintain its momentum? Read on. We also attempt to identify the key drivers of active equity hedge funds.